The "rate of cure" is the rate at which crosslinking, and the development of the stiffness (modulus) of the compound occur after the scorch point. As the compound is heated past the scorch point, the properties of the compound change from a soft plastic to a tough elastic material required for use. During the curing step, crosslinks are introduced, which connect the long polymer chains of the rubber together. As more crosslinks are introduced, the polymer chains become more firmly connected and the stiffness or modulus of the compound increases. The rate of cure is an important vulcanization parameter since it in part determines the time the compound must be cured, i.e., the "cure time". In the manufacture of vulcanized rubber articles, significant cost savings can be realized through a reduction of time the article is required to spend in the mold. Through enhanced rates of cure, the mold time required to meet minimum "states of cure" can be reduced.
The preparation of hydroformylated rubbers has been described in the prior art. For example, the hydroformylation of diene based polymers was disclosed in Ramp et al, J. Polymer Sc., Part A-1, 4, 2267-2279 (1966). In addition, the chemical modification of polybutadiene via homogeneous hydrogenation and hydroformylation was discussed in Mohammodi et al, Polymer Preprints, 27, No. 2, (Sept. 1986). Whereas these polymers are known, there has yet to be any practical utility for these compounds.
After extensive research, it has been discovered, that the hydroformylated rubber may be used to shorten the rates of cure of a sulfur vulcanizable rubber. This new use not only broadens the applications for hydroformylated rubber but enhances the cure of vulcanizable rubber in the absence of imparting undesirable properties to the vulcanizate.